Friday, December 13, 2013

Below are some points which I want to remember always J . Plan is to write
such point from each chapter. I hope it will help others.

Recovery time Objective - > uptime of server.

·99.9% -> 8.76 hours in year

·99.99% -> 53 minute in year

·99.999%-> 6minute in year

Recovery Point Object- > calculation of RPO depends on-

·Amount of data lost

·Cost to the company of lost data

·Cost to the company for the time to recover
data.

SQL server mirror
- > As per
TechNet this feature is going to be removed from future version , plan to use
“AlwaysOn Availability group “.Mirroring is implemented on a per-database basis and works only with
databases that use the full recovery model.

Database
mirroring maintains two copies of a single database that must reside on
different server instances of SQL Server Database Engine. Typically, these
server instances reside on computers in different locations. Starting database
mirroring on a database, initiates a relationship, known as a database mirroring session, between these server
instances. Database mirroring involves redoing
every insert, update, and delete operation that occurs on the principal
database onto the mirror database as quickly as possible. Redoing is
accomplished by sending a stream of active transaction log records to the
mirror server, which applies log records to the mirror database, in sequence,
as quickly as possible. Unlike replication, which works at the logical level,
database mirroring works at the level of the physical log record. Beginning in
SQL Server 2008, the principal server compresses the stream of transaction log
records before sending it to the mirror server.

Sql Server Clustering : two or more SQl Server node that act as a
single Sql server instance. A Sql server cluster contains –